On 23 September 2016 at 18:17, Amina Shahzadi wrote:
| Hello Dirk, Adler and Rcpp Colleagues
|
| Would you please guide me why the following code is giving the error of "
|
| cannot convert 'arma::subview_elem1<double, arma::mtOp<unsigned int,
arma::mtGlue<unsigned int, arma::mtOp<unsigned int, arma::Col<unsigned int>,
arma::op_rel_noteq>, arma::mtOp<unsigned int, arma::Col<unsigned int>,
arma::op_rel_noteq>, arma::glue_rel_and>, arma::op_find_simple> >' to 'double'
in initialization"
|
|
| The problem is in double alpha1 and double beta1.
The _core_ of the error message is reasonably clear: you cannot assign a arma
type (of some sort ... here stemming of the subsetting) to a double.
Solution: use as_scalar() -- see the Armadillo documentation for more -- ie
use these three lines at the core of your loops:
double alpha1 = as_scalar(alpha.elem(find(index !=i && index !=j)));
double beta1 = as_scalar(beta.elem(find(index !=j && index !=j)));
a(i) = exp(alpha1+beta1);
Dirk
|
|
|
| The code is:
|
| #include <RcppArmadillo.h>
| using namespace Rcpp;
| using namespace RcppArmadillo;
| //[[Rcpp::depends(RcppArmadillo)]]
| //[[Rcpp::export]]
|
| // A example of indexing some elements of a vector
|
| arma::vec Vec_Index(arma::vec alpha, arma::vec beta)
| {
| int m = alpha.size();
| arma::uvec index(m);
| arma::vec a(m);
| for(int i=0; i<m; i++)
| {
| index(i) = i;
| }
| for(int i=0; i<m; i++){
| for(int j=0; j<m; j++){
| double alpha1 = alpha.elem(find(index !=i && index !=j));
| double beta1 = beta.elem(find(index !=j && index !=j));
| a(i) = exp(alpha1+beta1);
| }
| }
| return a;
| }
|
|
|
|
|
|
|
|
|
| On Thu, Sep 15, 2016 at 2:52 AM, Avraham Adler <avraham.ad...@gmail.com>
wrote:
|
| Amina and I continued the conversation off list, but for closure purposes,
| the "multiple" version was tweaked a bit as there was comparison between
| signed and unsigned ints which did not throw an error for me, but did for
| Amina. Final multiple version posted below.
|
| Thanks,
|
| Avi
|
|
| #include <RcppArmadillo.h>
| using namespace Rcpp;
| using namespace RcppArmadillo;
| using namespace arma;
| //[[Rcpp::depends(RcppArmadillo)]]
|
| //[[Rcpp::export]]
| vec Sample_Exp_Multi(size_t n, vec alpha, vec beta) {
| size_t m = alpha.size();
| vec answers(n);
| uvec2 S;
| for (size_t i = 0; i < n; ++i){
| do {
| S = randi<uvec>(2, distr_param(0, m - 1));
| } while (S(0) == S(1));
| answers(i) = exp(alpha(S(0)) + beta(S(1)));
| }
| return(answers);
| }
|
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|
|
|
|
| --
| Amina Shahzadi
--
http://dirk.eddelbuettel.com | @eddelbuettel | e...@debian.org
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